Cathode inductive heating circuit



Feb. 14, 1939. w. F. EIAMES CATHODE INDUCTIVE HEATING CIRCUIT Filed Sept. 3, 1937 Z M 4 M U 2 Hwy N F F H 36 3 I F 2 2 0 a m Z In 0 m w 2y 4 4 2/ 7 E a Z a \Q H 5 2 @6 E t Q Z ZWQ 3 3 RM Y ma m m 0 W w I -A d Wm WITNESSES:

Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE CATHODE INDUCTIVE HEATING CIRCUIT Pennsylvania Application September 3, 1937, Serial No. 162,249

4 Claims.

My invention relates to electron discharge devices and especially to the cathode heating circuit for said electron discharge devices.

An object of my invention is to provide cathode excitation for an electron tube where a high current at low voltage is required for the filament.

Another object of my invention is to eliminate as far as possible seals through the glass casing of discharge devices of conductors carrying high currents.

Other objects and advantages of my invention will be apparent from the following description and drawing, in which:

Figure 1 is a view in cross-section through a discharge device embodying my invention;

Fig. 2 is a view in section taken on lines III I of Fig. 1;

Fig. 3 is a View in cross-section taken on line IIIIII of Fig. 1; and

Fig. 4 is a diagrammatic illustration of a circuit embodying my invention.

In certain types of tube installations, a cathode is required having an excitation at high current, but at very low voltage. Such a requirement may, for instance, be for a current of 15 to 20 amperes at 2 to 2 volts. Such a device presents a problem of sealing current leads through the casing that will operate at the small voltage and yet be able to withstand the high current therethrough. This problem is especially acute where the tube design has to be restricted to a small volume. In accordance with my invention, I incorporate in the container itself an inductive winding connected to the cathode and adapted to excite the cathode by means of a primary winding on the exterior of the casing.

In Figs. 1 through 3, I have disclosed a preferred embodiment of my invention in which the container I0 is preferably of the usual glass material forming the container wall. The anode I I, which may be of any desired form, is located within the container and has a conductive lead l2 secured through the container to the contact cap l3. The bottom l4 of the container I0 is preferably of thick glass and also preferably has a flat interior surface 15. In the bottom portion of the container is a core iii of high permeability iron. Surrounding this core are a plurality of turns ll of an inductive winding. The core and windings are adapted to rest on the flat bottom portion I 5 of the tube. The ends l8 and I9 of the core are preferably shaped so as to fit rather closely with the adjacent walls of the container 20 and 2|, respectively, and to conform thereto in contour. If desired, projections 22 from the container wall may be located just above the upper edge of the core to keep it in position in the container. Standards 23 are preferably connected with the ends of the core and these standards support and are connected to the cathode 24. This cathode may be of any suitable type, but I prefer to utilize a coiled filament as shown and preferably to coat it with strontium and barium oxide. The cathode connection 25 for the anodecathode current I prefer to seal through the bottom portion M of the tube to the mid-point 26 of the inductive windings 11. Other points of connection, of course, may be utilized, if desired.

The primary winding 21 on the exterior portion of the casing I prefer to mount on a core 28 of high permeability iron. This core is preferably of a yoke-shape having legs 29 with two projections 30 and 3| adapted to fit closely about the bottom portion of the glass container l0 and to have their adjacent edges 32 and 33 spaced from the edges l8 and IQ of the interior core but very little more than the wall of the container.

The number of turns illustrated in these figures are not obviously to scale. As a preferred illustration and not in a limiting sense, the number of turns on winding 21 or a l10-volt circuit might be 660 turns, and the turns on the winding I! would be twelve if approximately 2 volts were desired in the cathode heating circuit. The exterior core could be moved away from the interior core if such adjustment is desired.

In Fig. 4, I have illustrated two tube devices connected in a preferred circuit to provide fullwave rectification for a load 34. The energy for the cathode excitation is derived from lines 35 and 36 and apply to the coils 21 which are in in-- ductive relation with the coils l1 within the tube Hi. The energy or the cathode-anode circuit is derived from lines 31 and 38 connected to the primary 39 of a transformer 40 having its secondary winding 4| with its ends 42 and 43 connected to the anodes II and its mid-point 44 connected to one end of the load 34. The other end of the load is connected to the connection 45 extending from one cathode circuit 26 to the other cathode circuit of the other tube.

It will be noted that by my construction I provide a high amperage heating current for the cathode at very low voltage and yet the container merely has two leads therethrough for the anode and the cathode connections. It is apparent, of course, that additional electrodes, such as the ordinary control grid or additional well known types of auxiliary electrodes, may also be incorporated in these tubes.

Many other modifications may be made in the preferred embodiment of my device and accordingly I desire only such limitations to be imposed on the following claims as is necessitated by the prior art.

I claim as my invention:

1. An electron discharge device comprising a container, an anode and cathode within said container, a magnetic core made of two separate units, one of said units being wholly contained nected to said cathode, and a primary winding outside said walls.

3. An electron discharge device comprising a container, an anode and cathode within said container, a magnetic core made of two separate units, one of said units being wholly contained within the walls of said container, a heating circuit for said cathode comprising a secondary winding on the last-mentioned unit and connect ed to said cathode, and a primary winding outside said walls, the other said unit being linked by said primary winding, and having ends adapted to fit closely said walls opposite the ends of the core Within the tube.

4. A discharge device comprisng a container, a metal core wholly contained within the walls of said container, an inductive winding on said core, a cathode having its ends connected to said inductive winding and an anode cooperating with said cathode.

WILLIAM F. EAlVHilS. 

